Picked up a Wicked 8 for one of my Les Pauls from Scott. Really digging it. Fat and aggressive with excellent clarity and cleans up really well. Shot a quick clip (shitty iphone clip)
Probably best to check with @scottosan for the details. I've never tried the SD Alt 8 but from what I have read it's just a JB with an alnico 8 magnet and not a special wind.
I personally wanted something for my Chubtone that was a little fatter, bigger etc... than the JB as I'm trying to stay in the same realm tonally as my Les Pauls and PRS guitars loaded with Ceramic mags but I didn't want to go down the ceramic path this time. Since my Chub is an all mahogany body the JB was nice, but didn't have the girth I was looking for to be tonally in the same "range" as my Pauls and PRS's. His wicked 8 is a fat, big sounding pup but with some harmonic sweetness of the JB...at least to me, I like it.
It not based on the JB, but rather uses high wind 43awg bobbins instead of true JBs 44awg. Mine is 14.4K vs the the JBs 17k, but it’s the wind count and magnet that determine output more than resistance. The wind counts are similar, maybe less than 10% lower on my wicked 8.